The statements in this section merely provide background information related to the present disclosure and may not constitute prior art.
A vehicular automatic transmission includes a torque converter and a power train as a multi-stage transmission mechanism connected to the torque converter. The automatic transmission includes a hydraulic control system for selectively operating any one operation element among operation elements of the power train according to a driving state of a vehicle.
The hydraulic control system for the automatic transmission is configured to regulate a hydraulic pressure generated from an oil pump to a constant line pressure through a regulator valve, and then to control the adjusted pressure by a linear solenoid valve again to supply the controlled pressure to a coupling element constituted by a clutch and a brake.
However, in the hydraulic control system in the related art, when the supplied hydraulic pressure corresponds to a plurality of required hydraulic pressures, the maximum required hydraulic pressure of the linear solenoid valve is set to the maximum required hydraulic pressure, and when the coupling element is operated with the required hydraulic pressure of low pressure, driving current of the linear solenoid is suppressed, thereby controlling an appropriate output hydraulic pressure.
However, in the case of controlling an output hydraulic pressure while suppressing drive current of the linear solenoid valve as described above, a drive current control range is narrowed until the output hydraulic pressure is controlled to the required hydraulic pressure of low pressure, and as a result, the control of the output hydraulic pressure may not be efficient.
The above information disclosed in this section is only for enhancement of understanding of the background of the disclosure and therefore it may contain information that does not form the prior art that is already known in this country to a person of ordinary skill in the art.